LLYWELYNof Llangewydd (or Llewelyn Sion) (1520?–1616), Welsh bard, born about 1520, was a disciple of Thomas Llewelyn of Rhegoes [cf. Llewelyn, Thomas, 1720?-1793] and Meirig Dafydd of Llanishen, both in Glamorganshire. Sion Mowddwy, a contemporary, says he was an usher in the Glamorgan court of great sessions, but he gained his living mostly by transcribing Welsh manuscripts for Glamorganshire gentlemen, and had access to the libraries at Raglan, Y Vann, and other places. About 1575 he is mentioned under the name Lewelyn John by Sir Edward Mansel in his 'History of the Norman Conquest of Glamorgan,' as a learned and diligent collector of Welsh manuscripts. Llywelyn died in 1616. He presided at the session ('gorsedd') of the bards of Glamorgan at Tir Iarll in 1580, and was commissioned to collect and to reduce to writing the traditional lore of that bardic order. These were utilised by Iolo Morganwg (Edward Williams) in the preparation of his 'Cyfrinach y Beirdd,' published after his death by his son Taliesin Williams in 1829. A further instalment, termed ' Barddas,' was printed with a translation for the Welsh Manuscript Society in 1862. Several of his compilations are published in Iolo MSS., and on them are based most of the pretensions of neo-druidism to the possession of esoteric doctrines of great antiquity. One of his manuscripts which Iolo Morganwg said he had copied from an original (since lost) contained an account of an ancient Welsh bardic alphabet, called Coelbren y Beirdd, of which a full account is given by Taliesin Williams in a work bearing that title (Llandovery, 8vo), but the genuineness of such an alphabet is open to the gravest doubt.